Windows 10 - Skype for Business - your speaker is muted

This is a solution and not a question - SOLVED!

The other day Skype came up with this maddening message "your speaker is muted":

* Sound works for everything BUT Skype

* Clicking the [unmute] button it shows does not actually unmute the speaker

* Clicking the ((speaker)) icon in a call dialog does not actually unmute the speaker

* Test button [>] in "Audio Devices" dialog does not make the test sound happen

* No audio from anything else Skype-ish

For me the problem was the Skype sound input to the Realtek Audio Mixer was muted. But, you don't see that if you just look at the Taskbar speaker dialog or the default sound dialog:

* Make certain Skype is up

* <right-click> the speaker/sound icon in the taskbar

* [Open Volume Mixer]

You will now see the Skype for Business audio input to the sound mixer. And you should see a red circle on the speaker. Note you really MUST have Skype running or the Skype entry in the mixer dialog does NOT appear.

* Click the speaker - the red dot should disappear

And now your Skype session has audio again.

Have a better day - oh, unless you don't like Skype meetings, which I don't...